The Coalition's plan will provide mothers with 26 weeks' paid leave, at full replacement wage up to an annual salary of $150,000 (or a maximum of $75,000) – or the minimum wage if it is greater.

This strategy of ''wage replacement'' is fundamentally different to Labor's $1.8 billion scheme, introduced in January 2011. This provides mothers the minimum wage for 18 weeks.

There have long been concerns within the Coalition about Mr Abbott's scheme, with some MPs arguing the scheme is too generous in the current economic climate. Nationals MPs in particular are reported to be critical of the scheme, which they argue does not cater to stay-at-home mothers, particularly in regional and rural communities.

In Geelong on Tuesday, Mr Abbott insisted that his scheme was ''fully funded'' and ''fully costed''.

''I want to make it absolutely crystal clear that our paid parental leave scheme is good for our economy and good for our society,'' he told reporters.

On Tuesday, Mr Joyce, who has recently stepped down from his Queensland senate seat to contest the lower house, said the Nationals were behind the parental scheme.

''The Coalition policy has been announced by Tony and we support it,'' he said. ''The [shadow] cabinet stands behind it.''

''We work in a businesslike relationship with our Liberal Party colleagues for a consistent platform to take to an election.''

''That is a policy which we took it to the last election. It’s a policy that we confirmed in this election. We consider it to be very important economic reform for Australia.''

The Coalition's scheme would be partly funded by a 1.5 per cent levy on companies with a taxable income over $5 million, but on Tuesday, Senator Cormann would not be drawn on what percentage of the scheme's cost the levy would cover.

"Of course I know how much according to our costings . . . the paid parental leave levy will raise,'' he said. ''In good time before the election, we will be releasing all of the detailed costings and all of the detailed savings measures.''

On Monday, Mr Abbott conceded that the Coalition still needed to speak to the states to strike an agreement to partly fund the scheme, amid government claims of a $1 billion a year hole in the costings.

Mr Abbott told reporters he was confident that there was ''more than enough time'' before the July 2015 start date to reach agreement with the states on sharing the funding for the federal scheme.

But West Australian Premier Colin Barnett didn't hesitate in making his feelings clear, saying on Monday that the scheme was overly-generous. By Tuesday, Mr Barnett has changed his tune, saying he now supported Mr Abbott's scheme.

On Tuesday, a WA government spokeswoman confirmed that the federal Coalition had provided clarification of details of the scheme overnight.

''We understand that under the scheme, the Coalition would fund the gap between the current state schemes and the Coalition's 26-week scheme, and the WA government would co-operate,'' she said.

On Monday, Mr Barnett had said that while he supported paid parental leave, he thought Mr Abbott's scheme was too generous.

''If Tony Abbott becomes prime minister and that scheme is introduced, we will co-operate in terms of the administration, but we will not be contributing money to the scheme . . . as has been suggested.''

Queensland Premier Campbell Newman said Mr Abbott's assurance that the scheme would carry no net costs for Queensland was ''good enough for us''.

Mr Newman said he had been advised the state would be asked to ''make the same contribution that we would have made for our hard-working employees'' and no more under the federal Opposition Leader's scheme.

''And that is why I am happy to back this great initiative for working women in particular, that's why I'm prepared to back Tony Abbott 100 per cent and that is why I condemn the Labor Party, who are all over the shop with their views on women in the workplace,'' Mr Newman said in question time on Tuesday.

He said there would be no cuts to any state service to pay for the scheme.

NSW Premier Barry O'Farrell later also said that he supported the plan.

''It is very good news for working mothers,'' Mr O'Farrell said in a statement. ''I look forward to working with (Mr Abbott) on its implementation if he's elected.''

South Australian Labor Premier Jay Weatherill also said the state would not commit to the scheme before learning the details, saying Mr Abbott owed the state the courtesy of communicating about his plans.

''I haven’t heard anything from Mr Abbott about this. I don't think there's even been a piece of correspondence,'' Mr Weatherill said.

''I understand that we're being asked to make a contribution but I'd like to see what the nature of the detail is. I also don’t know what else he is proposing to cut to fund his promise of paid parental leave.''

Mr Weatherill said if proposed cuts had an adverse impact on South Australia it wouldn't make sense for the state government to endorse the policy.